This invention relates to improvements in rail fastening systems where rails are elastically fastened to rail ties. In particular this invention relates to rail fastening systems utilizing concrete rail ties.
Conventionally rails are held to rail ties by rail clips or fasteners which bear down on the rail flange. A rail pad located beneath the rail and composed of elastomeric material such as rubber, polyurethane, ethylvinylacetate or high density polyethylene insulates the rail from the rail tie. This pad has a field side on the outer side of the rail and gauge side on the inner side of each rail.
Concrete rail ties have been found to be prone to wear particularly in sandy locations. This invention is partly predicated on discovering the cause of this wear. As each loaded bogey passes over the tie, the rail pad deflects vertically and thus acts as a shock absorber. However, due to the poissons ratio of the materials used the pad must also deflect horizontally which means that every vertical load pulse causes the pad face to slide horizontally over the concrete tie.
In normal use this causes slight wear to the pad and practically no wear to the concrete face. However, in the presence of sand particles the grains of sand imbed themselves into the relatively soft pad material and slide on the concrete face. The same particles cut the concrete paste in the mortar causing abrasion to the concrete paste and mortar which can shorten the working life of the concrete rail tie.